1. Field of the Invention
The present invention generally relates to a cooling arrangement for all terrain vehicles. More particularly, the present invention relates to an engine cooling arrangement for use in all terrain vehicles.
2. Related Art
All terrain vehicles are often operated in open terrain under difficult running conditions. While such vehicles often may have unrestricted size, it is desirable to decrease the size and weight of the vehicle. For instance, a smaller vehicle allows its operator to maneuver into locations previously unreachable by the larger vehicles. Moreover, decreasing the size and weight of the vehicle increases the power to weight ratio of the vehicle as well as increases the fuel economy of the vehicle.
In the past, in some all terrain vehicles, the cooling systems have employed a cooling pump that is positioned under a forward portion of the crankcase. The cooling pump is used to circulate coolant between a radiator and an engine. The cooling pump was, in such applications, driven by connecting an input shaft to a crankshaft. The connection of the input shaft to the crankshaft might include a reduction gear train.
With the introduction of variable belt drive transmissions to all terrain vehicles, the transmission was positioned to a side of the engine and extended between the crankshaft and the engine output shaft. Because of the positioning of the transmission components, the crankcase had to be enlarged to accommodate both the transmission components and the cooling pump input shaft and its drive. Therefore, it became difficult to reduce the size of the crankcase while employing both a cooling pump and a variable speed transmission.
Moreover, due to the environments in which all terrain vehicles are used, the water pump had to be located in a protected location. Accordingly, the pump had to be positioned in locations that would not subject the water pump to abuse by environmental elements. For instance, the water pump would be positioned low within the crankcase to reduce the likelihood of inadvertent contact with passing elements. This position, however, led to maintenance difficulties.
There, thus, was a need for a water pump positioned for protection yet easily accessible for service and maintenance. Additionally, the water pump was preferably positioned so as to take advantage of the existing drive components of the engine while not interfering with the operation of the components. Moreover, the water pump was preferably positioned so as to allow the crankcase""s overall lateral footprint to be reduced.
Accordingly, one aspect of the present invention involves an all terrain vehicle comprising a frame, a seat mounted to an upper portion of the frame, at least one front wheel and at least one rear wheel connected to the frame. An engine transmission assembly and an engine are preferably mounted within the frame. The engine has a cylinder block, a cylinder head assembly attached to the cylinder block and a crankcase cover attached to the cylinder block generally opposite the cylinder head assembly. The transmission assembly contains, in part, transmission for driving the vehicle. A cooling pump is preferably attached to a side of the engine transmission assembly. A crankshaft is mounted for rotation within a crankcase generally defined by the cylinder block and the crankcase cover. Moreover, the engine transmission assembly preferably includes a balancer shaft driven off the crankshaft, and a cooling pump drive driven off the balancer shaft wherein the cooling pump drive has a rotational speed slower than a rotational speed of the balancer shaft.
Another aspect of the present invention involves an all terrain vehicle comprising a frame and an engine mounted to the frame. The engine generally comprises a cylinder block including a piston mounted for reciprocation within the cylinder block. A connecting rod is connected to the piston. The engine also comprises a crankshaft having at least one throw with the throw of the crankshaft being connected to the connecting rod. The crankshaft is preferably positioned within a crankcase with one end of the crankshaft carrying a flywheel magneto. The other end of the crankshaft is preferably connected to a clutch. A cooling pump is preferably positioned rearward of the crankshaft and connected to the crankshaft through a gear train.